Which of the following are true of database administration? $($Check all that are true.$)$

a$.$

A database administrator's managerial roles include enforcing policies, procedures, and standards.

b$.$

A DBA is responsible for selecting DBMS$,$ tuning the DBMS$,$ tuning SQL$,$ but not operating the DBMS$,$ which is the responsibility of the system operators.

c$.$

DBAs are responsible for ensuring the integrity, security, and privacy of data in databases.

d$.$

DBAs define strategic policies related to the data in the enterprise, and these policies are implemented by Data Administrators.